The present invention relates to a method and an apparatus for measuring capacitances, and specifically relates to a method and an apparatus for measuring capacitances between electrodes of an ink-jetting head, etc.
To emit ink-particles from ink-jetting head, expanding/shrinking actions of PZTs (Piezoelectronic ceramic) are utilized. Such expanding/shrinking actions are generated by applying an electronic field to each electrode attached to the PZT, which constitutes each of ink-chambers of the ink-jetting head. FIG. 6 shows an outer structural view of ink-jetting head 10. Surface A, indicated by the arrow in FIG. 6, servers as an ink-emitting surface on which nozzles (not shown in the drawings) are arranged. Electrode 1, for applying the electronic field to the PZT, is disposed at a former stage of each of the nozzles, and the ink-particles are emitted from the nozzles by controlling the electronic field applied to electrode 1.
FIG. 7(a) and FIG. 7(b) show an explanatory illustration for explaining the principle of the ink-emitting action. As shown in FIG. 7(a), both sidewalls, which constitute the ink-chamber of the ink-jetting head, can be deformed in concave-wise by applying the electronic field onto electrode 1 attached to PZT 4 of the both sidewalls. Then, when the electronic field returns to zero, the both sidewalls restore its original shape, as shown in FIG. 7(b), resulting in an emitting action of the ink-particle from nozzle 3 due to change of the physical pressure occurring at the same time.
In the abovementioned operation for controlling the emitting actions of the ink-particles, it is necessary that the accuracy of form at the PZT portion, as shown in FIG. 7(a) and FIG. 7(b), is unified in every nozzles, in order to emit uniform ink-particles from each of the nozzles. When the accuracy of form at PZT portion is unified, capacitances between electrodes are equal relative to each other. Accordingly, a measurement of capacitances between electrodes has been conducted to investigate the shape of the PZT portion.
Conventionally, one capacitance-measuring device has been employed for measuring capacitances between electrodes, by sequentially contacting a mono-probe with each of plural electrode rows.
In the abovementioned conventional method, the mono-probe should contact the electrode at the same number of times as the number of the electrodes, and has required a total measuring time defined by,
[total measuring time]=[measuring time for one electrode]xc3x97[number of electrodes].
Accordingly, it is an object of the present invention to shorten the time required for measuring each of capacitances between electrodes included in a plurality of electrode rows. For this purpose, a multi-probe contacts a plurality of electrode rows as one lump contact, and contacting-terminals corresponding to each of the electrode rows are divided into a predetermined number of groups, and capacitance-measuring devices, each of which is equipped for each of the groups, measure the capacitances between electrodes in each of the groups in parallel with the other groups by sequentially switching the contacting-terminals included in each of the groups. Concretely speaking, for instance, when the number of the electrode rows is eight, two capacitance-measuring devices measure the capacitances between electrodes in parallel by using the multi-probe having eight probes, which are divided into two groups, while sequentially switching outputs. Further, for instance, when the number of the electrode rows is sixteen, two capacitance-measuring devices measure the capacitances between electrodes in parallel by using the multi-probe having sixteen probes. Therefore, it is possible to shorten the time required for measuring by increasing a number of probes of the multi-probe, a number of scanners and also a number of capacitance-measuring devices, corresponding to a number of the electrode rows.
Accordingly, the abovementioned object of the present invention can be attained by capacitance-measuring methods and capacitance-measuring apparatus described as follow.
(1) A method for measuring capacitances, comprising the steps of: contacting a multi-probe with a plurality of electrode rows as one lump contact, wherein plural contacting-terminals of the multi-probe are divided into a plurality of groups, each of which includes a predetermined number of contacting-terminals and corresponds to each of the electrode rows; and measuring the capacitances between electrodes in each of the groups in parallel with the other groups by sequentially switching the contacting-terminals included in each of the groups.
(2) The method of item 1, wherein alternate signals, employed for measuring the capacitances in each of the groups, are supplied from a single alternate signal source.
(3) An apparatus for measuring capacitance, comprising: a multi-probe having a plurality of probes to contact a plurality of electrode rows as one lump contact, each of the probes contacting one of the electrode rows and a plurality of the probes being divided into a predetermined number of groups; a plurality of scanners, each of which corresponds to each of the groups, to sequentially switch contacting-terminals of a plurality of the probes; and a plurality of capacitance-measuring devices, each of which corresponds to each of the scanners, to measure capacitances between electrodes in all of the groups in parallel.
(4) The apparatus of item 3, further comprising: an alternate signal source to supply alternate signals having a measuring frequency to each of the capacitance-measuring devices
(5) The apparatus of item 3, wherein a measuring frequency of alternate signals to be supplied to each of the capacitance-measuring devices is established so as to minimize cross-interferences between the measuring frequency and a sampling frequency employed for a synchronized detection circuit.
(6) The apparatus of item 3, wherein lengths of wirings, each of which connects the multi-probe with each of the capacitance-measuring devices and corresponds to each of the electrode rows, are uniform.
(7) The apparatus of item 3, further comprising: a lighting device employing a diffusion-reflecting optical system to detect a fitting-mark for positioning, which is formed on a measuring object having a plurality of the electrode rows.
Further, to attain the abovementioned object, other capacitance-measuring methods and capacitance-measuring apparatus, embodied in the present invention, will be described as follow:
(8) A capacitance-measuring method, characterized by comprising the steps of,
contacting a multi-probe with a plurality of electrode rows as one lump contact;
switching a measuring-channel by means of a scanner; and
measuring the capacitances between electrodes in parallel by means of a plurality of capacitance-measuring devices.
According to the capacitance-measuring method cited in item 8, since the multi-probe contacts a plurality of electrode rows as one lump contact, and a plurality of capacitance-measuring devices measure capacitances between electrodes in parallel while switching the outputs of the multi-probe in a scanning mode, it becomes possible to shorten the time required for switching the electrodes.
(9) A capacitance-measuring apparatus, characterized by comprising:
a multi-probe to contact a plurality of electrode rows as one lump contact;
a scanner to switch outputs of the multi-probe; and
a plurality of capacitance-measuring devices to measure the capacitances between electrodes in parallel, outputted from the scanner.
According to the capacitance-measuring apparatus cited in item 9, since the multi-probe contacts a plurality of electrode rows as one lump contact, and a plurality of capacitance-measuring devices measure capacitances between electrodes in parallel while switching the outputs of the multi-probe in a scanning mode, it becomes possible to shorten the time required for switching the electrodes.
(10) The capacitance-measuring method recited in item 8, characterized in that the alternate signals, having the same frequency for measuring the capacitances, are fed to each of the measuring devices from a single alternate signal source.
According to the capacitance-measuring method cited in item 10, since the alternate signals, having the same frequency for measuring the capacitances, are fed to each of the measuring devices from a single alternate signal source, it becomes possible to reduce interferences in the measuring system in which a plurality of measuring devices perform capacitance-measuring operations in parallel.
Incidentally, the term of xe2x80x9cinterferencesxe2x80x9d, cited in the above, is defined as occurrence of measuring-errors caused by electromagnetic coupled voltages induced in a cable due to electronic currents flowing in other cables. When each of the capacitance-measuring devices individually has its own alternate signal source, interferences in the measuring system could be occur due to slight differences between the alternate signal sources, even if a measuring-instrument manufacturer had strictly performed the accuracy adjustment for every alternate signal source. Accordingly, the abovementioned configuration makes is possible to reduce interferences in the measuring system.
(11) The capacitance-measuring apparatus recited in item 9, characterized in that a single alternate signal source is employed for supplying the alternate signals, for measuring the capacitances, to a plurality of capacitance-measuring devices.
According to the capacitance-measuring apparatus cited in item 11, since the alternate signals, having the same frequency for measuring the capacitances, are fed to each of the measuring devices from a single alternate signal source, it becomes possible to reduce interferences in the measuring system in which a plurality of measuring devices perform capacitance-measuring operations in parallel.
Incidentally, the term of xe2x80x9cinterferencesxe2x80x9d, cited in the above, is defined as occurrence of measuring-errors caused by electromagnetic coupled voltages induced in a cable due to electronic currents flowing in other cables. When each of the capacitance-measuring devices individually has its own alternate signal source, interferences in the measuring system could be occur due to slight differences between the alternate signal sources, even if a measuring-instrument manufacturer had strictly performed the accuracy adjustment for every alternate signal source. Accordingly, the abovementioned configuration makes is possible to reduce interferences in the measuring system.
(12) The capacitance-measuring apparatus recited in item 9, characterized in that the measuring frequency of each capacitance-measuring device is set at such a frequency that the influence against the sampling frequency at a synchronized detecting circuit is minimized each other.
According to the capacitance-measuring apparatus cited in item 12, it is possible to reduce interferences when measuring capacitances.
In other words, according to the abovementioned configuration, even when each of the capacitance-measuring devices individually has its own alternate signal source, it is possible to eliminate an influence of the disturbance exerted onto output signals of the measuring system and also possible to eliminate an influence of the disturbance, which is n-times of the sampling frequency of the synchronized detecting circuit, by synchronized-detecting the frequency component applied to the measuring system.
(13) The capacitance-measuring apparatus recited in item 9, characterized in that a bridge-wiring is not at all used for wiring between the multi-probe and the capacitance-measuring apparatus.
According to the capacitance-measuring apparatus cited in item 13, since a bridge-wiring is not at all used, it becomes possible to suppress the variation of capacitances between measuring terminals, resulting in accurate measurement of capacitances.
This is because, when the wirings between outputting terminals of the predetermined number of groups are performed in the bridging mode of wiring, the stray capacitances between the wires would vary, since the lengths of the wires corresponding to each of electrode rows are not uniform. According to the abovementioned configuration, it is possible to eliminate such the variation of the stray capacitances, and it is not necessary to obtain compensating data for compensating the variation.
(14) The capacitance-measuring apparatus recited in item 9, characterized in that a diffusion-reflecting optical system is employed as a lighting optical system to detect a fitting-mark for recognizing a work position.
According to the capacitance-measuring apparatus cited in item 14, it is possible to attach contrasts to the fitting-marks for positioning, and thereby, it becomes possible to precisely detect the position of the electrodes.
Incidentally, although a coaxial drop-irradiating illumination has been employed as a lighting optical system for detecting the fitting-marks of the work position (the position of the ink-jetting head) in a general purpose probing device (mainly used for silicon wafers), contrasts have been hardly obtained in respect to the fitting-mark, for recognizing the position, which is formed by depositing aluminum onto the surface area having Ra (roughness) of around 0.5 xcexcm. The abovementioned configuration makes it possible to solve the problem mentioned above.